Heart and brain perfusion imaging before and after stimulation (e.g., dipyridamole and acetazolamide, respectively) is a clinically important procedure for the efficient care of patients with vascular diseases. Many different methods for imaging perfusion have been employed, ranging from x-ray computed tomography with inhaled stable xenon to transcranial Doppler ultrasound, but none has the attributes of resolution, quantitation, volume of organ coverage and widespread practical availability. This new project is to develop iodine-122 (3.6 min) positron emission tomography (PET) tracers particularly for heart perfusion by perfecting the rapid iodination chemistry and by technological improvements of the 122Xe/122I radioisotope generator, such that 122I-compounds can be reliably and automatically delivered. 122Xe (20 hr) availability from TRIUMF, Canada and potential availability from other accelerators has motivated this research project. Brain perfusion studies with 122I-HIPDM have been completed in 16 normal subjects, 5 Alzheimer s patients and one stroke patient. Cardiac perfusion agents will be selected from the best of 122I-labeled amphetaminium, piperazinium and imipraminium quaternary amines and rotenone classes of compounds after studies in red cell perfused rabbit heart preparations and dog PET studies. Comparisons of the selected compound will be made against 13NH and 62Cu-PTSM by dynamic PET in man.